1. Field
This disclosure relates to electrical connectors and, in particular, an electrical connector for light fixtures.
2. Background
The method by which light fixtures are electrically connected has undergone few changes over the years. Fixtures are fed with power in the form of armoured or flexible cables that are permanently affixed to ceiling junction boxes and to light fixtures with metallic or plastic connectors. These connections are made through an industry standard common knockout opening size of ⅞″ diameter in both ceiling junction boxes and fixtures. Depending on the fixture style, there will either be a few knockouts available at a designated splice area as in the example of downlights, or throughout the fixture body to afford convenient access as in the form of fluorescent fixtures that present a larger surface area. The cables will contain enough wires to provide one or more circuits depending on the application. Multi-lamp and dimming fluorescent fixtures will sometimes require more than one circuit to offer different levels of light output or to take advantage of energy savings by reducing the amount of light to suit application need.
Applying permanent wiring in the field is labour intensive and subject to a higher degree of failures and safety related issues as every termination represents a point of risk. Field conditions are much worse than that of a controlled manufacturing process line. Therefore, limiting the amount of terminations and exposure to risk should result in a higher degree of accuracy and safety. The same notion applies to future maintenance should the fixtures experience sub-component failure. Pluggable fixture connections enhance labour savings and increase safety. Making connections hot-pluggable result in further savings as electricians can energize circuits ahead of fixture mounting and determine fixture performance as they go. Once safely installed, a hot pluggable system does not require specialized labour to service, thereby reducing the costs of installation and maintenance. If fixtures fail to perform properly, one simply unplugs and replaces the faulty fixture with an operable fixture. Failures can be more easily addressed in a controlled environment on a test bench. This is much easier, safer, and more cost effective than shutting down complete circuits and trying to troubleshoot in the field. As electricians understand, troubleshooting can usually occur while one is on a lift in a dark environment. There is therefore a need in the art for a multi-circuit connector which can be mounted in a common knockout that can be safely hot-pluggable while power remains on.
Modular wiring options exist for manufacturers to provide factory wired receptacles on fixtures and cables that can be supplied separately with molded plug ends. Also available are cables with molded plugs which can be wired to the fixtures at the factory and connected to discrete receptacles that get mounted to ceiling junction boxes. An example of this is Canadian Patent No. 1,219,307, and modular wiring systems produced by Electec™. Drawbacks observed in the present state of the art are that custom openings are needed on fixtures or junction boxes to house molded receptacles, or receptacles mounted through standard knockout openings present extra dimension to the fixtures such that custom packaging becomes a requirement. The added profile also presents the opportunity for greater damage during transit and handling. Molded receptacles and plug cabling are offered in discrete circuit, voltage, and length formats that are inflexible to changing field requirements. If different circuiting, voltage, or different cable lengths are required at time of installation, the installer may have to wait for full manufacturing lead time or endure expensive field rewiring.
Connecting fluorescent fixtures to take advantage of multi-lamp electronic ballasts can also be a challenge. Consider that common fluorescent single lamp strip lights are inventoried with one ballast per fixture even though multi-lamp ballasts are available to drive four or more lamps. Reducing ballasts represents cost savings and in our example, saving three ballasts would be remarkable. There are significant barriers to take advantage of this. Safety organizations do not approve of the supply of incomplete products. Therefore, a contractor receiving empty strips and strips with multi-lamp ballasts would have to obtain field certification making the installation process more expensive to administer. Further, the savings in ballast reduction would be offset by the added labour cost in extra fixture wiring and complexity. An option exists to custom order from manufacturers, but again, savings are eroded by the extra administration and forethought required to engineer the needed products ahead of time along with extra lead time needed to manufacture. Flexibility is reduced as changes often experienced in the field may require another full lead time for custom supply. Last, fluorescent strip lights are sometimes mounted individually and sometimes row mounted end to end which requires mechanical connection of the end plates for feed through wiring of power wires and secondary wiring coming from the ballasts. Custom orders become more complex and inflexible as full system wiring must be provided by the manufacturer, whether individual or row mounted, to achieve safety approval.
There is a growing desire to connect energy saving control devices through which power is routed such as occupancy sensors, photo sensors, addressable relays, etc. An example of this is a class of fluorescent fixtures called highbays which are used to light large spaces with high ceilings such as warehouses and recreation facilities. Significant energy savings can often be realized with the use of an occupancy sensor that is mechanically connected to the knockout on the fixture end plates. The sensor turns lamps on when motion is detected within range of view and off after a period of time when motion is not detected. Sensors can be cumbersome to install in the field as the fixture has to be disassembled in order to bring wiring in for splicing and to mechanically connect the sensor through the knockout opening. This can also be done at the fixture manufacturing level, but more lead time is needed and it presents issues for shipping as sensors add significant dimension to the fixture profile making packing difficult and exposure to damage becomes greater. Present state of the art is to provide an occupancy sensor mounted to a junction box that in turn must be fastened to the fixture with the use of tools. A power cord is then plugged into a molded receptacle located on the junction box and in turn, a control wiring cord is then plugged into a molded receptacle located on the fixture. As with other modular wiring discussed above, the receptacle must be custom fit into the fixture. Multiple circuiting is not offered and would require a discretely different molded set of receptacles and plugs.
Considering the prior discussions of electrical quick connect systems, there are no systems that are made for standard dry area applications that can be easily converted to perform in wet applications.
Various devices have been utilized or proposed in order to remedy the aforementioned problems. U.S. Pat. No. 7,874,860 (Starke), U.S. Pat. No. 7,258,564 (Su) and U.S. Pat. No. 6,358,076 (Haag), for instance, are examples of twist-lock mechanisms that serve to secure electrical connections. Haag's device is an electrical connector which can be secured by an independently turning sleeve. On the other hand, Su's device is a more simplistic connector whereby the metal connector itself is twisted thus locking it in place. Meanwhile, Starke's device comprises two connectors, which can be connected to one another and secured by a threaded sleeve. While these devices provide easy to connect mechanisms to create and facilitate a continuous electrical connection, the fact of the bare metallic connectors extending from the plug causes a risk of shock for an installer if improperly handled. Further, such devices are not designed to fit within smaller, standardized ⅞″ knockouts common in the lighting industry. As such, a twist-lock device would need to be utilized which could overcome, or at least minimize this risk and be sufficiently small to fit within a standard knockout.
Other devices have been proposed in order to facilitate installation of sensors onto light fixtures. U.S. Pat. No. 7,637,766 (Kauffman et al) and U.S. Pat. No. 5,593,318 (Bilson et al) are examples of such inventions. Bilson's device relates to an electrical receptacle that attaches itself to a luminaire housing, and provides a plurality of electrical contact channels. A photo controller can be fastened to the receptacle by means of a clamp member which is joined to the housing by means of a threaded fastener. Kauffman's receptacle includes similar functions but is fastened to the housing by means of a spring clamp. Unfortunately, these inventions do not allow specific use within a common ⅞″ knockout universal to many fluorescent fixtures, and are not designed to make live multiple circuits up to 600V.
As such, there is a need for an electrical connector, with a positive lock capability, that can overcome the drawbacks elaborated herein, while still making it easy, affordable and convenient to install and quickly connect new luminaire housings, or to add control devices (such as a motion sensor) immediately or at a later date of the installation. These features of the invention will be apparent from review of the disclosure, drawings and description of the invention below.